1. Technical Field
The present invention relates to radiation-hardened circuits in general, and in particular to a single-event upset hardened ring oscillator.
2. Description of Related Art
When a high-energy particle impinges upon an integrated circuit (IC) device, the high-energy particle ionizes the regions of the IC device through which it travels. This ionization creates mobile charges in the vicinity of the high-energy particle's travel path, thereby generating a transient pulse, and the transient pulse may produce a Single Event Upset (SEU) within the IC device. An SEU may change critical data and/or alter the processing state of an IC device. Depending upon severity, an affected circuit or device may require a power reset in order to recover from an SEU.
Conventional ring oscillators are vulnerable to SEUs. An SEU is less likely to occur if the magnitude of its associated transient pulse is significantly less than the magnitude of regular signals within an IC device. Thus, one way to minimize SEU susceptibility is by using large-area devices that generally operate using larger magnitude signals. However, large-area devices consume more power and necessitate higher manufacturing costs.
Consequently, it would be desirable to provide an SEU hardened ring oscillator with minimal circuit redundancy, which can be manufactured by using conventional IC fabrication techniques.